1. Field of the Invention
The present invention relates to a color developer composition, and an aqueous dispersion, recording sheet and color developing ink obtained by using the same.
2. Description of the Related Art
Examples of pressure-sensitive recording sheets include an upper sheet prepared by applying on one surface of a base material microcapsules comprising therein a capsule oil dissolving an electron donative developing compound (color former) and the like, an intermediate sheet prepared by applying on one surface of a base material a color developer (electron receptive compound) which develops color in contact with an electron donative developing compound and by applying on the opposite surface microcapsules, and a lower sheet prepared by applying on one surface of a base material a developer, and in general, they are used in a combination of upper sheet-lower sheet or upper sheet-intermediate sheet-lower sheet.
Further, there is also a copy sheet in the form of a single body which can effect copying with a single sheet, prepared by applying on the same surface of a base material microcapsules and a color developer.
Conventionally, salicylic acid derivatives, for example, polyvalent metal salts of 3,5-disubstituted salicylic acid derivatives (e.g., Japanese Patent Publication (JP-B) No. 51-25174), or polyvalent metal salts of a salicylic acid resin obtained by reacting salicylates with styrenes to obtain salicylate resins, hydrolyzing the salicylate resins, then, allowing polyvalent metal compounds to act on the hydrolyzates (Japanese Patent Application Laid-Open (JP-A) No. 1-133780), have been known to be useful as a developer (electron receptive compound) for a pressure-sensitive recording sheet.
However, these pressure-sensitive recording sheets containing a polyvalent metal salt of a salicylic acid derivative as a color developer have problems that color developing speed, particularly color developing speed at lower temperature environment is slow, and a longer period of time is necessary for obtaining a recording image having practically sufficient color-developed concentration.
For solving these problems, various trials have been suggested. For example, a composition containing a metal salt of an aromatic carboxylic acid, and a. carboxylic amide (JP-A No. 2-215582), a composition obtained by dissolving a polyvalent metal salt of a salicylic acid derivative into vegetable oil and an organic solvent having a boiling point of 200xc2x0 C. or lower, and emulsifying the solution in water (JP-A No. 4-52184), a composition composed of a polyvalent metal salt of a salicylic acid derivative, and a polyoxyalkylene or derivative thereof (JP-A No. 6-15951) and the like have been suggested.
However, it can not be admitted that the color developing speed of a color developer obtained by these known methods, particularly, the color developing speed at lower temperature is satisfactory. Further, when a color developer prepared by using known methods is treated in the form of an aqueous dispersion, there are problems that dispersion stability is often poor, precipitation and aggregation occur.
An object of the present invention is to provide a color developer composition which has excellent dispersion stability and manifests excellent color developing speed, and an aqueous dispersion, recording sheet and color developing ink obtained by using the same.
The present inventors have intensively investigated a color developer composition, and an aqueous dispersion, recording sheet and color developing ink thereof and resultantly completed the present invention. Namely, the present invention relates to
(i) A color developer composition comprising (A) a color developer containing a polyvalent metal salt of a salicylic acid derivative, and (B) a polyester polyol having in the molecule skeleton at least one carbonate bond or ester bond, and a derivative thereof;
(ii) The color developer composition according to (i) wherein the polyester polyol and derivative thereof is a polycarbonate diol or lactone-based polyester polyol;
(iii) The color developer composition according to (i) or (ii) wherein the content of the component (B) is from 1 to 25 parts by weight based on 100 parts by weight of the component (A);
(iv) An aqueous dispersion of a color developer composition prepared by dispersing a color developer composition according to any of (i) to (iii) in water;
(v) A recording sheet having on a base material a layer containing a color developer composition according to any of (i) to (iii);
(vi) A recording sheet obtained by applying on a base material a coating solution prepared by using an aqueous dispersion of a color developer composition according to (iv);
(vii) A color developing ink comprising a color developer, photocurable compound, photopolymerizing agent and pigment wherein the color developer is a color developer composition according to any of (i) to (iii); and
(viii) A recording sheet obtained by printing using a color developing ink according to (vii) on a base material.
It has become possible, according the present invention, to provide a color developer composition, aqueous dispersion, recording sheet and color developing ink, having excellent dispersion stability and manifesting excellent color developing speed.